VULNERABILITY OF AGRONOMIC SYSTEMS IN BULGARIA

In recent years the problem of climate and its variations under the influence of natural processes and factors of anthropogenetic origin has come to the forefront of scientific and practical problems on a world-wide scale. Climate change vulnerability assessments of agronomic systems in Bulgaria have been initiated. In this paper preliminary results of this study are presented. Different climate change scenarios were defined. Global circulation model (GCM) scenarios and incremental scenarios for Bulgaria were created and applied. The influence of climate change on potential crop growing season above a base of 5° and 10 °C in Bulgaria was investigated. Increases in temperature can be expected to lengthen the potential growing season, resulting in a shift of thermal limits of agriculture in Bulgaria. The Decision Support System for Agrotechnology Transfer (DSSAT) Version 2.1 was used to assess the influence of climate change on grain yield of maize and winter wheat. Maize and winter wheat yields decreased with increasing temperatures and decreasing precipitation.     

Bemerkungen zu den «Januar-Singularitäten» der Konzentration atmosphärischer Gefrierkerne

Zusammenfassung Messungen der Gefrierkernkonzentration während der Jahre 1957 und 1958 zeigten im Verlauf des Monats Januar markante Spitzenwerte, die zeitlich mit den vonE.G. Bowen vorhergesagten Maxima übereinstimmten. Da es große Schwierigkeiten bereitet, das Auftreten dieser Maxima durch die «Meteorstaubhypothese» zu erklären, wird auf Umstellungen der Zirkulation der Atmosphäre im Januar hingewiesen, die möglicherweise diese Schwankungen der Gefrierkernkonzentration auslösen können.

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Summary Investigations on freezing nuclei show characteristic anomalies of the concentration during January 1957 and 1958. These anomalies fit in the schedule predicted byE.G. Bowen for the occurrence of high values of freezing nuclei. Since the explanation on the basis of the meteor-dust theory appears difficult, fluctuations of the atmospheric circulation during January may be responsible for the peak-values of the freezing nuclei concentration.

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The research reported in this article has been sponsored and supported in part by the Geophysics Research Directorate, Air Force Cambridge Research Center, ARDC, under contract AF 61 (514)-927 through the European Office, ARDC.     

Thermodynamik und Kinematik des Kaltluftföhns

Zusammenfassung Unter Zugrundelegung der Theorie des südalpinen Föhns vonH. Ficker werden der Kaltluftföhn der argentinischen Kordillere, der Polarluftföhn des Tessins und die Bora der mittleren Apenninen behandelt. Drei Phasen kennzeichnen den Kordillerenföhn. Eingeleitet durch Tropikluftföhn folgen Polar- und Antarktikluftföhn; erst der letztere dringt bis zur Niederung durch. Der Kaltluftföhn des Tessins wird entsprechend der Theorie vonH. Ficker durch die instabile Phase der abgehobenen Warmluft eingeleitet, auf die der Absturz der Kaltluft in die Niederung erfolgt. Die Tramontana der Apenninen zeigt in ihrer Hauptphase einen ausgeprägten Tropopausentrichter mit sehr niedriger Tropopause. Kinematisch ist wichtig, daß die stationäre Leewellenströmung des Polarluftföhns und noch ausgeprägter die Tramontana häufiger hochreichende Stratosphärenwellen entwickeln können.

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Summary TakingFicker's theory of the South-Alpine foehn as a base the author investigates the cold air foehn of the Argentine Cordillera, the polar air foehn of Ticino (Switzerland) and the bora of the Central Apennines. Three phases characterize the foehn of the Cordillera. After the initiation by tropical air foehn the phases of polar air and antarctic air foehn follow and only the last named can penetrate to the bottom of the valleys. The cold air foehn of Ticino is initiated in accordance to the theory ofFicker by the instable phase of the lifted warm air which is followed by the downfall of the cold air to the valley. The tramontana of the Apennines in its main phase shows a pronounced tropopause funnel with extremely low tropopause. From the point of kinematics it is important that the stationary lee-wave flow of the polar air foehn and, still more pronounced, of the tramontana frequently can develop high reaching stratospheric waves.

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Résumé En partant de la théorie établie parH. Ficker pour le foehn au sud des Alpes, on examine le foehn d'air froid de la Cordillère argentine, le foehn d'air polaire au Tessin et la Bora des Apennins moyens. Trois phases caractérisent le foehn de la Cordillère. Il débute par un afflux d'air tropical suivi par de l'air polaire, puis par de l'air arctique. Ce n'est que ce dernier courant de foehn qui pénètre jusque dans les vallées. Le foehn d'air froid du Tessin débute, selon la théorie deFicker, par la phase instable de l'air chaud soulevé. Ce n'est qu'ensuite que cet air froid se précipite dans les vallées. La Tramontane des Apennins est accompagnée dans sa phase principale d'une sorte d'entonnoir dans la tropopause qui s'abaisse alors fortement. Il est important de retenir, du point de vue cinématique, ques les ondulations stationnaires sous le vent du foehn d'air polaire, et encore plus de la tramontane, peuvent souvent développer des ondes atteignant de grandes altitudes dans la stratosphère.

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Mit 15 Textabbildungen     

The ocean as source or sink of reactive trace-gases

Summary After a brief review on recent experimental work on the uptake resp release of SO₂ and NH₃ by the ocean, new results on the distribution of these reactive trace-gases in the marine atmosphere are presented. In the case of SO₂ there is no doubt that the ocean acts as a sink. In the case of NH₃ new observations and calculations show that under certain conditions the ocean may be a NH₃ source.     

Verification of Carbon Sink Assessment: Can We Exclude Natural Sinks?

Any human-induced terrestrial sink is susceptible to the effects of elevated atmospheric CO₂ concentration, nitrogen deposition, climate variability and other natural or indirect human-induced factors. It has been suggested in climate negotiations that the effects of these factors should be excluded from estimates of carbon sequestration used to meet the emission reduction commitments under the Kyoto Protocol. This paper focuses on the methodologies for factoring out the effects of atmospheric and climate variability/change. We estimate the relative magnitude of the non-human induced effects by using two biosphere models and discuss possibilities for narrowing estimate uncertainty.     

Forest cover: setting targets for the future

The International Year of Forests, declared by the UN, is a good occasion to discuss approaches to reducing forest degradation in developing countries. The articles collected in Thematic Forest Series form a diversity of ideas which is essential for setting the levels below which the countries' reduced emissions could be measured and credited. This editorial calls attention to the use of Land-Use/Land-Cover Change models.     

Climatically Driven Minimum of Energy Demand for Heating in Cities at the Center of the European Part of Russia

Izvestiya, Atmospheric and Oceanic Physics - The minimum energy consumption in cities of the Russian Plain is largely determined by climatic conditions, because residential heating in winter is a...